Controlled environment light fixture

ABSTRACT

Controlled environment light fixture configurations include an LED light source. The light fixtures can be installed and removed from below the ceiling. The light fixture can be installed and removed without opening the lens frame of the light fixture. The light fixture includes a sealed housing and seals to the ceiling when installed. The light fixtures are provided in exterior dimension sizes that allow the fixtures to be installed in a variety of controlled environment ceilings in recessed configurations. The lower surface exposed to the controlled environment is free of welds and grinds in order to provide a corrosion resistant surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is divisional application claiming priority to patentapplication Ser. No. 15/867,187 filed Jan. 10, 2018, U.S. Pat. No.10,584,866 dated Mar. 10, 2020, which is a divisional applicationclaiming priority to U.S. Pat. No. 9,897,305 dated Feb. 20, 2018, whichclaims the benefit of U.S. Provisional Patent Application No. 61/992,859filed May 13, 2014; the disclosures of each are incorporated herein byreference.

BACKGROUND OF THE DISCLOSURE 1. Technical Field

This disclosure relates to light fixtures for controlled environmentswhich include clean rooms, containment areas, surgical suites, andhazardous locations. The light fixture forms a seal between thecontrolled environment and the plenum environment and can be installedfrom below the ceiling of the controlled environment. The exemplarylight fixture configurations are recessed within ceiling openings, sealto the lower surface of the ceiling structure, can be installed frombelow, and can support weight from above.

2. Background Information

Light fixtures for controlled environments such as clean rooms,containment rooms, surgical suites, and hazardous locations must befabricated from inert materials, provide sealing functions, as well asproviding desirable lighting properties. Controlled environment lightfixtures are typically powered by an external power source and thus mustprovide a hermetically-sealed pathway for the power wires. The designersand users of controlled environments often want the light fixtures to bebuilt into and recessed within the ceiling instead of hanging down fromthe ceiling support structures. These light fixtures must form aparticulate and fluid impervious seal between the controlled environmentand the plenum environment above the ceiling when the light fixture isinstalled. Standards and tests such as those defined by the NationalSanitation Foundation protocols, the Medicines and Healthcare ProductsRegulatory Agency (MHRA) requirements, the National EnvironmentalBalancing Bureau procedures must be met by components used in clean roomconstruction.

The controlled environment can be located at any of a variety offacilities and the light fixture should be configurable for a variety ofuses. For example, the light fixture may be used for applications suchas pharmaceutical, biotech, biosafety, semi-conductor, surgical suite,and research facilities. The designers and users of these controlledenvironments desire light fixtures that can be configured with differentlight engines as well as providing a high quality, reliable seal.Different light distribution patterns are also desired for differentapplications. The light fixtures should be easy to install as well asbeing easy to maintain.

SUMMARY OF THE DISCLOSURE

Controlled environment light fixture configurations using LED lightengines are disclosed. The light fixture configurations seal to theceiling of the controlled environment, are easy to install, and maintainthe LEDs in a sealed enclosure during use. The light fixtures areprovided in sizes that fit multiple ceiling types.

In one configuration, the light fixture is sealed to the lower surfaceof the ceiling with a gasket having a first portion disposed between ahousing of the light fixture and the lower surface of the ceiling. Alens frame of the light fixture engages a second portion of the samegasket to seal the enclosure of the light fixture. A single gasket isused to seal the enclosure to the ceiling and the lens frame to theceiling. The single gasket can be carried by an outer flange of thehousing.

In one configuration, the LED light fixture is configured to be usedwith a variety of ceiling types including 2.0″ T-bar grid ceilings forcontrolled environment applications. The light fixtures are provided insizes that fit the standard-size light openings for the 2.0″ T-bar gridceilings which allow the light fixtures to be used with other ceilingconfigurations as well.

In one configuration, the light fixture includes an LED light sourcethat is mounted directly to the aluminum housing of the light fixture.The housing functions as the heat sink for the LED light source with theheat being transferred by conduction because of the direct connectionbetween the two elements. The housing can include an integral LEDmounting element.

In one configuration, the housing of the light fixture functions as aheat sink for the LED circuits that are mounted directly to the housingto provide cooling by way of conduction. The exemplary configuration ofthe housing includes an extruded envelope that functions as the LEDmount and the integral heat sink for the LEDs. The ends of the envelopeare received in slots defined by end caps with a seal disposed in theslots to define a sealed housing for the enclosure of the light fixture.

In one configuration, the light fixture can be installed from below thecontrolled environment ceiling without removing the lens frame of thelight fixture. The mounting hardware is accessible from the exterior ofthe light fixture from below the fixture. The person installing thelight fixture does not have to remove the lens frame in order to accessthe mounting hardware. The installer only needs to remove caps from thelens frame to access the mounting hardware. The caps are then replacedto seal the interior of the light fixture.

In one configuration, the light fixture locates the power supply for theLED light source within the enclosure. When the power supply is disposedwithin the enclosure, an electrical connector is provided that providesa quick connect plug-type connection between the LED power supply andthe line power supply line providing electrical power to the lightfixture. In another configuration, the LED power supply is disposedoutward of the enclosure.

In one configuration, the lens frame has a room-facing stainless steelsurface that is free of welds and grinding so the exposed face of thelens frame is resistant to corrosion from cleaning and disinfectingprocesses that occur in the controlled environment. The lens frameperimeter element is formed by deep drawing and trimming the stainlesssteel material.

In one configuration, the lens frame is secured to the envelope of thelight fixture with connectors disposed near the perimeter of the lightfixture close to the sealing gasket. These connectors terminate insidethe enclosure of the light fixture. The connectors can be received inself-centering nuts carried by the enclosure.

In one configuration, the light fixture housing has an overall height ofabout two inches. The light fixture can be recessed within a two inchthick ceiling. One configuration can be mounted on top of a ceiling gridand one configuration can engage the lower surface of a ceiling grid. Inthese configurations, the light fixture lens frame extends down onlyshort distance such as less than 0.75 inches and defines no right anglesurfaces to the ceiling.

In one configuration, a support plate can be used above the enclosure ofthe light fixture to allow a person to walk on the support platedirectly over the light fixture. The support plate can be a metalsupport plate such as a stainless steel or aluminum diamond platematerial that extends outwardly from the perimeter of the light fixtureto be self-supported on the ceiling support structure to allow at leastone worker to stand directly above a light fixture above the ceiling.

In one configuration, the light fixture has a symmetric/asymmetric lightdistribution pattern. This LED light fixture can be used for thecontrolled environment of a surgical suite.

The preceding non-limiting aspects, as well as others, are moreparticularly described below. A more complete understanding of theprocesses and equipment can be obtained by reference to the accompanyingdrawings, which are not intended to indicate relative size anddimensions of the assemblies or components thereof. In those drawingsand the description below, like numeric designations refer to componentsof like function. Specific terms used in that description are intendedto refer only to the particular structure of the embodiments selectedfor illustration in the drawings, and are not intended to define orlimit the scope of the disclosure

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom perspective view of an exemplary light fixtureinstalled in a controlled environment ceiling.

FIG. 2 is a top perspective view of FIG. 1.

FIG. 3 is a perspective view looking into the enclosure for theexemplary light fixture of FIG. 1.

FIG. 4 is a perspective view looking down onto the top of the exemplarylight fixture of FIG. 1.

FIG. 5 is a perspective view looking up at an exemplary lens frame.

FIG. 6 is a perspective view looking down onto the top of the exemplarylens frame of FIG. 5.

FIG. 7 is a section view showing the installation of the exemplary lightfixture.

FIG. 8 is an enlarged view of the encircled portion of FIG. 7.

FIG. 9 is a perspective view of the edge lit LED light engine beinginstalled in the enclosure.

FIG. 10 is a perspective view of another step of the installation of theLED light engine being installed.

FIG. 11 is a section view showing the light fixture installed in aceiling.

FIG. 12 is a view looking up at the light fixture installed in aceiling.

FIG. 13 is an enlarged view of the gasket that forms the seal betweenthe lens frame and the ceiling.

FIG. 14 is a perspective view looking down on an alternative lightingfixture installed in a ceiling.

FIG. 15 is a perspective view looking up into the enclosure of FIG. 15.

FIG. 16 is a perspective view of the top of another exemplary lightfixture for a controlled environment ceiling.

FIG. 17 is a bottom plan view (one looking up at the light fixture) ofthe light fixture of FIG. 16 mounted in a ceiling.

FIG. 18 is a perspective view looking into the enclosure of the lightfixture of FIG. 16.

FIG. 19 is a perspective view of the mounting arm of the light fixtureof FIG. 16.

FIG. 20 is a perspective view of the light fixture of FIG. 16 with themounting arms extended.

FIG. 21 is a section view taken through the middle of the envelope.

FIG. 22 is a perspective view looking up at the corner of the enclosure.

FIG. 23 is a section view showing the position of the gasket that isdisposed between the flange and the lower surface of the ceiling whenthe light fixture is installed.

Similar numbers refer to similar parts throughout the disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A first exemplary embodiment of a light fixture that can be used in acontrolled environment such as a clean room is indicated generally bythe reference numeral 2 in the accompany drawings. These light fixturesalso can be used in ceilings other than those for controlledenvironments. For example, there are some ceilings where mounting alight fixture from below is desirable and some where there is littlehead room above the ceiling to receive the light fixture. Light fixture2 is adapted to be recessed within an opening defined by ceiling 4 andto seal to a lower surface of ceiling 4. Ceiling 4 can be any of avariety of ceiling types used in controlled environment constructionincluding, but not limited to, drop ceilings that use T-bar supportgrids and drop panels, panel systems that can be walkable, and flatceilings such as gypsum ceilings. Although the T-bar support grids forcontrolled environment ceilings usually have upwardly disposed sealswhich support panels, light fixture 2 has a seal configuration thatengages the downward facing surface of the T-bar which is part of thelower surface of ceiling 4. Light fixture 2 generally includes a housing6, a lens frame 8, and a light engine 10. Once installed in ceiling 4,light fixture 2 forms a seal between the controlled environment belowlight fixture 2 and the plenum environment above light fixture 2.

In this description, the directions up and down, upward and downward,upper and lower, as well as above and below, are with reference to aceiling in a controlled environment with the light fixtures disposedsubstantially horizontal with the controlled environment below the lightfixture and the plenum disposed above the light fixture. The termoutward refers to a direction from the interior of the light fixturetoward the exterior of the light fixture.

Light fixture 2 may be provided in a variety of sizes and shapesincluding rectangles and circular frames. The rectangular frames may besized for what is commonly called a 1×4, 2×2, and 2×4 foot lightopenings. These descriptions reference the approximate sizes of thelight openings defined by a grid ceiling system. Light fixture 2 isconfigured to prevent moisture and air leakage by sealing to the lowersurface of the ceiling structure when the light fixture is installed.The light fixture enclosures are sized to fit 2.0″ T-bar grid size lightopenings for controlled environment ceilings and thus can be used inother ceiling applications such as panel and gypsum ceilings withoutmodification. For example, the 1×4 light fixture has an enclosure depthabove the lower surface of the ceiling of 2.0 inches and a 0.625 inchheight below the lower surface of the ceiling. The mounting arms extendhigher and can extend up to 4.687 inches above the lowermost surface oflight fixture 2. The overall length is 47.937 inches with an overallwidth of 11.937 inches so that light fixture 2 will engage the lowersurfaces of the 2.0″ T-bar grid. Housing 6 has a length of 45.437 inchesand a width of 9.437 inches to fit within an opening of 9.75 inches by45.75 inches defined by the 2.0″ T-bar grid. For example, the 2×2 lightfixture has an enclosure depth above the lower surface of the ceiling of2.0 inches and a 0.625 inch height below the lower surface of theceiling. The mounting arms extend higher and can extend up to 4.687inches above the lowermost surface of light fixture 2. The overalllength is 23.937 inches with an overall width of 23.937 inches so thatlight fixture 2 will engage the lower surfaces of the 2.0″ T-bar grid.Housing 6 has a length of 21.437 inches and a width of 21.437 inches tofit within an opening of 21.75 inches by 21.75 inches defined by the2.0″ T-bar grid. For example, the 2×4 light fixture has an enclosuredepth above the lower surface of the ceiling of 2.0 inches and a 0.625inch height below the lower surface of the ceiling. The mounting armsextend higher and can extend up to 4.687 inches above the lowermostsurface of light fixture 2. The overall length is 47.937 inches with anoverall width of 23.937 inches so that light fixture 2 will engage thelower surfaces of the 2.0″ T-bar grid. Housing 6 has a length of 45.437inches and a width of 21.437 inches to fit within an opening of 45.75inches by 21.75 inches defined by the 2.0″ T-bar grid.

In one exemplary configuration, light engine 10 includes an edge lit LEDpanel 20 as the light source for the light fixture, a power supply 22,and power cord 24 as well as the electrical connections between powersupply 22 and the LED circuit boards. In other configurations, lightengine 10 can include an LED light source configured for direct lightingor indirect lighting. In one example of direct lighting, the LED lightsource of light engine 10 output their light in a directionsubstantially perpendicular to lens frame 8. In an example of indirectlighting, light engine 10 includes LEDs that output light in a directsubstantially parallel to lens frame 8. In the indirect lightingconfigurations, reflectors are used inside housing 6 to reflect lightout trough lens frame 8. In any of these configurations, a diffuser canbe used for the light entering lens frame 8 or the lens of lens frame 8can diffuse the light. The LEDs can be provided in a variety of lumenoutputs and colors as well as being dimmable.

Power cord 24 passes through housing 6 and the pass-through location ishermetically sealed with a seal 26 or a through connector 26 that formsa hermetic seal. A benefit of light fixture 2 is that light engine 10can include commercially available edge lit LED panels. Another benefitis power supply 22 is individual to panel 20 and can be contained withinhousing 6 above panel 20. When power supply 22 is disposed withinhousing 6, a quick-connect electrical connector can be used to form theelectrical connection between power cord 24 and the power supply 22 oflight engine 10. In other configurations, power supply 22 can bedisposed outside housing 6.

Housing 6 generally includes a base wall 30, a continuous sidewall 32,and an upwardly-facing mounting surface that seats under ceiling 4 whenlight fixture 2 is installed. The upwardly-facing mounting surface canbe provided on a variety of structures that form part of housing 6 sucha flange or flanges, a channels, a beam, or a projection regardlesswhether it is solid or hollow. In the exemplary configuration depictedin the drawings and described herein, a flange 34 projects from sidewall32 and defines the upwardly-facing mounting surface. All seams andcorners between these walls and the flange are closed and sealed todefine a one piece, sealed enclosure body. Housing 6 can be made fromaluminum, galvanized steel, stainless steel, or a polymer. When housing6 is formed from metal, the seams and corners can be welded so that noair can pass through the seams or corners. In the exemplaryconfiguration, housing 6 is rectangular and includes four corners thatare welded closed. Housing 6 can be made from aluminum with weldedcorners and an unplasticized PVC finish. The corners of housing 6 alsocan be sealed with a sealing material placed at the exterior of thecorners. Sidewall 32 has a height that provides a depth to housing 6sufficient to receive light engine 10. Sidewall 32 may be configured foruse with a two inch ceiling panel. Flange 34 extends outwardly from thelower edge of sidewall 32 and also may have welded corners. Flange 34 isconfigured for the ceiling installation. Flange 34 can be configured towork with 1.5 inch or 2.0″ T-bar ceilings. Flange 34 can be configuredfor a gypsum ceiling with a two inch U-channel.

Housing 6 is secured to ceiling 4 with a plurality of swing arm mountbrackets 40. Each bracket 40 includes a post 42 that extends throughbase wall 30 to support a mounting arm 44 having a portion that can bemoved over ceiling 4 as shown in FIG. 8. Mounting arm 44 is initiallydisposed over base wall 30 so that housing 6 can be moved up into anopening defined by ceiling 4 from below. The installer then moves eachmounting arm 44 over ceiling 4 by rotating post 42. After mounting arm44 is disposed over ceiling 4 and housing 6 is supported by mountingarms 44, the installer tightens brackets 40 to clamp a gasket 50 carriedby flange 34 against the lower surface of ceiling 4. This isaccomplished by rotating posts 42 until they are tight. Post 42 isthreaded through bracket 40 so that post 42 can be rotated to tightenflange 34 against ceiling 4. In an optional configuration, mounting arm44 can be configured to engage the corner of housing 6 between sidewall32 and base wall 30 so that the installation cannot be over tightened(shown in FIG. 8). A seal 46 seals the opening in base wall 30 thatreceives post 42. In the alternative configuration of FIG. 14, swing armmounting brackets 40 include cammed mounting arms 48. Each of cammedmounting arms 48 can be rotated to a position where it is entirelydisposed above base wall 30 and a plurality of other positions where arm48 is disposed over ceiling 4. The ceiling-facing surface of cammedmounting arm 48 defines a cam having a ramped thickness so that theclamping force is increased as post 42 is turned. Rotation of cammedmounting arms 48 pull flange 34 up toward ceiling 4. Mounting brackets40 allow housing 6 to be installed from below ceiling 4.

In another configuration of housing 6 that is installed with access toenclosure from above, no portion of mounting brackets 40 extends throughhousing 6. These brackets 40 are manipulated and tightened from above.

Light fixture 2 uses a single gasket 50 disposed over the end of flange34 to provide the seal between ceiling 4 and the exterior of housing 6.This gasket 50 is compressed between ceiling 4 and flange 34 as shown inFIGS. 8 and 13 when mounting brackets 40 are tightened. As describedbelow, gasket 50 also defines the seal between housing 6 and lens frame8. Gasket 50 can be an extruded, U-shaped gasket with opposed legs thatslide over flange 34. Gasket 50 can be vulcanized. Gasket 50 can be madefrom a NSF-approved material. Gasket 50 can be a closed cell foammaterial. Gasket 50 can be a vulcanized rubber. Gasket 50 can beextruded or molded in an elongated shaped. The ends of gasket 50 arespliced with the corner locations notched so gasket 50 can be bentaround the corners of housing 6. Gasket 50 also can be formed from aplurality of individual sections that are spliced at the corners ofhousing 6. Gasket 50 can be secured to flange 34 with an adhesive or bya friction fit.

Lens frame 8 is used to enclose light engine 10 within housing 6. Lensframe 8 includes a lens 60 that allows light to pass through. Lens 60 iscarried by frame 62 that defines a lip 64 having an upper surface thatengages gasket 50 when lens frame 8 is connected to housing 6. Lip 64 isangled upwardly toward ceiling 4 when lens frame 8 is installed anddefines a smooth sealing surface that engages gasket 50. The engagementof lip 64 with gasket 50 also helps hold gasket 50 against ceiling 4.

Lens 60 may be 0.187″ clear tempered glass, 0.125″ clear high impactacrylic, 0.125″ amber high impact acrylic, or other materials as desiredfor a particular application. Lens 60 can be used to disperse the lightfrom light engine 10 or to tint the light.

Lens frame 8 defines a slot 66 that receives the edge of lens 60. Slot66 is defined by a cantilevered arm 68. The connection between perimeterframe 62 and lens 60 is sealed. The seal can be formed with a tape suchas a very high bond (VHB) tape which can be a closed cell foam acrylictape. Other sealing materials and structures can be used to seal lens 60to frame 62. Frame 62 can be made from overlapping 18-gauge stainlesssteel (Type 304 and Type 316). Lip 64 can be defined by a 60 degreebeveled edge. The corners of frame 62 are welded (TIG welded and groundsmooth). Frame 62 can have a 2B finish that is passivated (theprotective oxide layer on stainless steel has been restored orregenerated after the parts have been fabricated or welded). Frame 8also can have an unplasticized PVC finish that is anti-microbial. Frame62 also can be made from extruded aluminum that is anodized. The cornersare closed to form a seal. Frame 62 also can be made from plastic.

Lens frame 8 is mounted to housing 6 with a plurality of fasteners 70that are received in bosses 72 disposed inwardly of the portion ofgasket 50 disposed under flange 34. Bosses 72 may be carried by flange34. Bosses 72 may be threaded nuts that threadedly receive fasteners 70.Bushings may be used with the connection between fasteners 70 and bosses72. The bushings can be Teflon®. Fasteners 70 can be flush with theexterior of frame 62 when tightened. Lens frame 8 can provide a secondseal to light fixture 2 that seals the interior of housing 6.

Light engine 10 is mounted to housing 6 by connecting one edge of lightengine 10 to mounting brackets 80 one on side of housing 6 with clips 84that allow light engine 10 to pivot down away from housing 6. The otherside of light engine 10 is secured to mounting brackets 82 with threadedfasteners 86. These connections do not extend through housing 6 andprovide for quick mounting and dismounting of light engine 10 withinhousing 6. In another configuration, housing 6 is provided with a basewall 30 that swings up to allow light engine 10 to be installed andserviced from above.

A support plate such as a diamond plate metal can be used over the topof housing 6 to allow workers to walk on the top of housing 6 when suchweight support is desired.

A second exemplary embodiment of a light fixture that can be used in acontrolled environment ceiling is indicated generally by the referencenumeral 102 in FIGS. 16-23. Light fixture 102 is adapted to be recessedinto an opening defined by a ceiling 104. Ceiling 104 can be any of avariety of ceiling types used in controlled environment ceilingconstruction including, but not limited to, drop ceilings that use T-barsupport grids and drop panels such as 2.0″ T-Bar grids, panel systemsthat can be walkable such as 5×10 ceiling panels, and flat ceilings suchas gypsum ceilings. Light fixture 102 generally includes a light engineand an enclosure. The enclosure dissipates heat from the LEDs, impedesleakage from the plenum while facilitating stringent cleaning protocols(NSF Protocol P442), provides IP66 ingress protection for the enclosure(IEC60598), minimizes surface contamination (NSF2), and operates safelyin hazardous locations (Class I, Division 2). The enclosure includes ahousing 106 and a lens frame 108 that is connected to and sealed tohousing 106 to define a sealed environment for at least the LEDs of thelight engine. When installed in ceiling 104, light fixture 102 forms aseal between the controlled environment below light fixture 102 and theplenum environment above ceiling 104 that carries light fixture 102.

Light fixture 102 may be provided in a variety of sizes and shapesincluding rectangles and circular frames. The rectangular frames may besized for what is commonly called a 1×4, 2×2, and 2×4 foot lightopenings. These descriptions reference the approximate sizes of thelight openings defined by a grid ceiling system. Light fixture 102 isconfigured to prevent moisture and air leakage by sealing to the lowersurface of the ceiling structure when the light fixture is installed.The light fixture enclosures are sized to fit 2.0″ T-bar grid size lightopenings for controlled environment ceilings and thus can be used inother ceiling applications such as panel and gypsum ceilings withoutmodification. For example, the 1×4 light fixture has an enclosure depthabove the lower surface of the ceiling of 2.0 inches and a 0.625 inchheight below the lower surface of the ceiling. The mounting arms extendhigher and can extend up to 4.687 inches above the lowermost surface oflight fixture 102. The overall length is 47.937 inches with an overallwidth of 11.937 inches so that light fixture 102 will engage the lowersurfaces of the 2.0″ T-bar grid. Housing 106 has a length of 45.437inches and a width of 9.437 inches to fit within an opening of 9.75inches by 45.75 inches defined by the 2.0″ T-bar grid. For example, the2×2 light fixture has an enclosure depth above the lower surface of theceiling of 2.0 inches and a 0.625 inch height below the lower surface ofthe ceiling. The mounting arms extend higher and can extend up to 4.687inches above the lowermost surface of light fixture 102. The overalllength is 23.937 inches with an overall width of 23.937 inches so thatlight fixture 102 will engage the lower surfaces of the 2.0″ T-bar grid.Housing 106 has a length of 21.437 inches and a width of 21.437 inchesto fit within an opening of 21.75 inches by 21.75 inches defined by the2.0″ T-bar grid. For example, the 2×4 light fixture has an enclosuredepth above the lower surface of the ceiling of 2.0 inches and a 0.625inch height below the lower surface of the ceiling. The mounting armsextend higher and can extend up to 4.687 inches above the lowermostsurface of light fixture 102. The overall length is 47.937 inches withan overall width of 23.937 inches so that light fixture 102 will engagethe lower surfaces of the 2.0″ T-bar grid. Housing 106 has a length of45.437 inches and a width of 21.437 inches to fit within an opening of45.75 inches by 21.75 inches defined by the 2.0″ T-bar grid.

In this description, the term “LED light source” includes a single LED,an array of LEDs, a plurality of LEDs, and any of these taken alone orcombined as a group on a circuit board or supporting member. As such,when the LED light source is said to be mounted to another element, thismeans both that (1) a circuit board carrying LEDs is mounted and that(2) the individual LED or LEDs are mounted.

In one configuration of the second exemplary configuration, the lightengine includes at least one LED light source 112 that includesplurality of individual LEDs 111 mounted to a strip-shaped circuitboard, a light guide plate 114, a power supply 122, a power cord 124,and the electrical connections between power supply 122 and strip 112.LED light source 112 is mounted vertically so that the light shining outof the LEDs 111 is directed sideways (parallel to the body of lens frame108) into the edge of light guide plate 114. Light guide plate 114 canbe disposed close to or directly against the LEDs 111. This ensures noindividual diode creates a bright spot viewable from below fixture 102and that essentially all of the light output by LEDs 111 is received bylight guide plate 114. A reflector 113 is integrally formed with ordisposed on or above the upper surface of light guide plate 114 toreflect light back towards lens frame 108. A light diffuser 115 isdisposed under light guide plate 114 or formed integrally therewith.Light diffuser 115 can be a separate plate member, a coating applied tolight guide plate 114, a surface treatment such as etchings made inlight guide plate 114, or members disposed within the body of lightguide plate 114. These options may be used in combination with eachother. In one exemplary configuration wherein light fixture 102 is usedin a controlled environment for a surgical suite, light guide plate 114and/or diffuser 115 provide an asymmetric/symmetric light distributionpattern for above the surgical table. Light guide plate 114, reflector113, and diffuser 115 can be carried by housing 106 or by lens frame108.

In other configurations, the light engine can provide a direct lit,up-lit, or back lit lighting configuration or a combination of thesewherein a light guide plate 114 is not used. In a direct litconfiguration, LED light sources 112 can be mounted directly toreflectors 116 or mounted in another location to output lightsubstantially perpendicular to lens frame 108. The light engine also canuse one or more indirect LED light sources 112 such as those that shineup and reflect the light off of reflectors 116 or LED light sources 112that output parallel to lens frame 108 and are reflected from reflectors116. LED light sources 112 can be provided in a variety of lumen outputsand colors and can be dimmable. Power cord 124 passes through housing106 and the pass through location is hermetically sealed with a seal 126or a through connector 126 that forms a hermetic seal. A benefit withlight fixture 102 is that one or more power supplies 122 provided forstrip 112 or strips 112 are contained within housing 106. When powersupply 122 is disposed within housing 106, a quick-connect electricalconnector can be used to form the electrical connection between powercord 124 and the power supply 122 of light engine 110. In otherconfigurations, power supply 122 can be disposed above housing 106 withthe power supply lines extending through the sealed connector 126.

Housing 106 generally includes an envelope 130 and a pair of end caps132. Envelope 130 and end caps 132 cooperate to define anupwardly-facing mounting surface that is disposed under ceiling 104 whenlight fixture 102 is installed. When ceiling 104 is a grid and panelstyle ceiling, the upwardly-facing mounting surface is disposed under aportion of the grids that define the light opening. The upwardly-facingmounting surface can be provided on a variety of structures that formpart of housing 106 such a flange or flanges, a channels, a beam, or aprojection regardless whether it is solid or hollow. In the exemplaryconfiguration depicted in the drawings and described herein, a flange134 projects outwardly about the entire perimeter of housing 106 todefine the upwardly-facing mounting surface. The upper surface of flange134 is disposed under ceiling 104 when light fixture 102 is installed.Flange 134 supports the gasket that seals light fixture 102 to theceiling.

Envelope 130 is a unitary body and is made from a material that conductsheat away from LED strips 112. The exemplary configuration providesenvelope 130 as an aluminum structure that functions as a conductiveheat sink for LEDs 111. LED strips 112 are mounted directed to LEDmounts 136 which are integral structures defined by envelope 130 so thatheat generated by strips 112 is transferred by conduction directly intothe body of envelope 130. LED mounts 136 can be members that projectdown from the inner surface of envelope 130 with the members definingsubstantially vertical mounting surfaces for LED circuit board strips112 as shown in FIG. 21. The vertical orientation of the mountingsurface positions the LEDs 111 horizontally to output lightsubstantially parallel to lens frame 108. In the exemplaryconfiguration, each mount 136 is in the form of a solid beam integrallyformed with envelope 130 such that it functions as a heat sink. The sideof mount 136 opposite to the vertical mounting surface is spaced fromthe sidewall of envelope 130 as shown in FIGS. 18 and 21 to define achannel to receive the drive shafts 204 of the swing arm mountingassemblies described below. Envelope 130 also defines a plurality ofheat fins 138 to increase the surface area of envelope 130 to transferthe heat out of envelope 130. Heat fins 138 are disposed immediatelyinward of mounts 136 just out of the way of the swing arm mountingassemblies 200 described below. When light guide plate 114, reflector113, and diffuser 115 are carried by housing 106, they can be mounted toLED mounts 136.

Each end cap 132 defines a channel 140 that receives an end of envelope130. A gasket 142 is disposed within channel 140 to create a sealedhousing 106. Gasket 142 can be poured-in-place or self-supportingindependent element that is added to channel 140 before the end ofenvelope 130 is inserted. Envelope 130 defines a plurality of channels144 that receive the self-tapping threads of threaded connectors 146that secure end caps 132 to envelope 130. In other configurations,different mechanical connectors can be used to secure end caps 132 toenvelope 130 or adhesives or welds can be used to secure the elementstogether. Tightening connectors 146 pull envelope 130 into channels 140against gasket 142 to define a hermetically sealed housing 106. Thisenclosure can be pressure tested and certified prior to the assembly oflight fixture 102. When light guide plate 114, reflector 113, anddiffuser 115 are carried by housing 106, they can be mounted to end caps132. This structure can be configured to support enough weight to bewalkable.

Envelope 130 and end caps 132 can be made from aluminum, galvanizedsteel, stainless steel, or a polymer. In one configuration, envelope 130is formed from an aluminum extrusion that allows the length of lightunit 102 to be defined by cutting the extrusion to the desired length.End caps 132 can be die cast aluminum. This allows the same extrusiondie to be used to form envelope 130 for a light fixture having differentlengths. The seam 148 shown in FIG. 19 depicts where the flange portionof end caps 132 abut the flange portion of envelope 130 to define thecontinuous upper surface of flange 134 that supports the gasket. Whenlight guide plate 114, reflector 113, and diffuser 115 are carried byhousing 106, they can be mounted to envelope 130.

End caps 132 define the height of housing 106 which can be configuredfor use with two inch thick ceiling panel system. This configurationprevents the body of light fixtures 102 from protruding up above theupper surface of a walkable ceiling which reduces tripping hazards. Inone configuration of the light fixture 102, the height of housing 106(excluding the swing arm mounting assemblies and connector 126) abovethe upwardly-facing mounting surface is no more than two inches.

Flange 134 extends about the entire perimeter of housing 106 and carriesthe gasket 160. FIG. 23 depicts the arrangement of gasket 160, flange134, lens frame 108, and ceiling 104. Gasket 160 provides a seal betweenthe upper surface of flange 134 and the lower surface of ceiling 104.Gasket 160 also defines a seal between the upwardly angled lip 162 oflens frame 108 and ceiling 104. Gasket 160 also defines a seal betweenflange 134 and lens frame 108. Gasket 160 includes a pair of legs 164spaced by a slot 166 that receives flange 134. An adhesive can be usedto secure gasket 160 to flange 134. Gasket 160 can be a vulcanizedrubber material.

Lens frame 108 is connected to housing 106 with a plurality of threadedconnectors 170 that extend up through lens frame 108 at locationsdirectly below flange 134 such that the threaded nuts 172 that receiveconnectors 170 are disposed outwardly of the side and end walls ofhousing 106 and close to angled lip 162 so that the force provided bytightening connectors 170 drives lip 162 into gasket 160. Connectors 170can be disposed directly under flanges 134 and the upper leg gasketportion 164 while the lower leg 164 of gasket 160 can be cut out toprovide room for the nuts 172 that receive connectors 170 or the lowerleg 164 can be disposed between nut 172 and flange 134. A seal is usedbetween each connector 170 and lens frame 108. The seal can be carriedby lens frame 108, connector 170, or provided as a separate element thatis added to connector 170. Nuts 172 are movably carried by housing 106below flange 134. Connector mounting members 174 project from the sidesof envelope 130 to define channels 176 under flange 134. A variety ofstructural members can be used for member 174 and a flange is depictedin the exemplary configuration. Connector mounting member 174 defines anopening, a notch, or a slot at each location of connector 170. Athreaded nut 172 is movably disposed at each of these locations suchthat connector 170 will engage and automatically center nut 172 duringassembly as connector 170 is tightened. Each nut 172 has a base 180 thatis larger than the opening, notch, or slot. Base 180 is movably disposedin channel 176 and supports a threaded boss 182 that threadedly receivesthe threaded end of connector 170. Each end cap 132 defines connectorsupport members 190 at the locations for nuts 172. The movableself-centering nuts help the user assemble lens frame 108 to housing 106because the user does not have to perfectly align each connector 170with each nut 172. Another feature that aids assembly is retainers 184that hold connectors 170 to lens frame 108 after connectors aredisconnected from nuts 172 to prevent connectors 170 from falling awayfrom lens frame 108.

Light fixture 102 can be mounted by a user disposed below ceiling 104.The electrical connection is made prior to placing light fixture 102 upinto the opening defined by ceiling 104. Another benefit provided bythis configuration of light fixture 102 is that the user does not haveto remove lens frame 108 to install or remove light fixture 102. Lightfixture 102 includes a plurality of swing arm mounting assemblies 200that allow the light fixture 102 to be secured to ceiling 104 frombelow. Each swing arm mounting assembly 200 includes a mounting arm 202that is driven back and forth between an extended position and aretracted position by a drive shaft 204 that extends into housing 106through a sealed opening in envelope 130. In the extended position, arm202 is disposed above flange 134 such that it is disposed over theportion of ceiling 104 that engages flange 134. In the retractedposition, arm 202 is disposed inward of flange 134 so that housing 106can be fit up into an opening or removed from an opening defined byceiling 104.

Each drive shaft 204 terminates within housing 106 above lens frame 108outwardly of mounts 136 that support LED strips 112. Lens frame 108defines access openings that are normally sealed with removable andreplaceable sealing caps 206. Caps 206 can be threaded, twist-lockedbayonet-style, or snap fit in place. During installation or removal, theuser removes caps 206 to access drive shafts 204. The user can thenrotate drive shafts 204 and thus mounting arms 202 with a tool such as asocket wrench, a hex wrench, or a screwdriver. Each cap 206 is disposedflush with the lower surface of lens frame 108 and is made from the sameinert material as lens frame 108 such as stainless steel. Each cap 206includes an integral seal that engages lens frame 108 to provide ahermetic seal when cap 206 is installed. The integral seal can be agasket or an O-ring that is secured to cap 206 so that it will reliablyengage the sealing seat defined by lens frame 108. The user thus onlyhas to remove caps 206 to operate swing arm assemblies 200. The user canthus install light fixture 102 without changing the engagement of lensframe 108 with gasket 160 which helps maintain a good water tight anddust tight seal for the interior of housing 106.

Each mounting arm 202 rotates with its drive shaft 204 until mountingarm 202 engages a stop 210. When mounting arm 202 is disposed against astop 210, rotation of drive shaft 204 adjusts the vertical position ofmounting arm 202 with respect to housing 106 which allows the lightfixture to be tightened to ceiling 104. In some configurations, eachmounting arm 202 includes an enlarged end 212 that engages housing 106to stop the adjustment to prevent overtightening. In someconfigurations, the enlarged end 212 is the portion of mounting arm 202that engages the stop 210. A spring such as a torsion spring disposedcan be disposed around drive shaft 204 to urge mounting arm 202 towardthe extended or retracted position. In another configuration, a springused to hold mounting arm upright. In one configuration, a coil springis disposed around drive shaft 204 between mounting arm 202 and housing106.

In the exemplary configuration, stop 210 is defined by a mounting tab220 that is connected to envelope 130. Mounting tab 220 can be used towire light fixture 102 to a structure above ceiling 104 if such supportwiring is desired. Mounting tab 220 includes a foot 222 that slides intochannel 144 defined by envelope 130. The sidewalls that define channel144 also define a neck that is narrow compared to the body of channelsuch that a foot having an enlarged head and narrow neck can slide downchannel 144 but cannot be pulled out vertically. Mounting tab 220 isfixed at this location by passing drive shaft 204 through mounting tab220. A second foot can be disposed parallel to foot 222 to engageenvelope 130 to support mounting tab 220.

Lens frame 108 generally includes a perimeter frame 230, a transparentlens 232, and caps 206. In some configurations, light guide plate 114,reflector 113, and diffuser 115 are also carried by lens frame 108. Lens232 is sealed to perimeter frame 230. When carried by lens frame 108,light guide plate 114, reflector 113, and diffuser 115 are supported ina position that aligns plate 114 with LED strips 112 when lens frame 108is connected to housing 106. Light guide plate 114 and lens 232 can beselected to provide desired lighting output in cooperation with LEDstrips 112. Light fixture 102 can be provided in 4000K, 5000K, and UVfiltering amber configurations.

Lens frame 108 includes the surfaces of light fixture 102 that areexposed to the controlled environment in which light fixture 102 isbeing used. In some configurations, disinfectants or other chemicals areused in the controlled environment and lens frame 108 must be configuredto not react with the materials. Mold treatment processes can corrodemetals and stainless steel surfaces that have been compromised bywelding or grinding. In one configuration of light fixture 102,perimeter frame 230 is formed from stainless steel. An 18 gaugestainless steel, type 304 or 316 can be used. Perimeter frame 230 isformed by a deep drawing and trimming fabrication method that does notdegrade the chromium at the surface of perimeter frame 230 that isexposed to the controlled environment. As such, a perimeter frame 230that is free of welds at the corners is provided for increase corrosionresistance. In some embodiments, all welding for stands to connect lens232 or other components are energized from the inside surface ofperimeter frame 230 with no room-side surface welding or grinding. Thisallows the entire exposed surface of perimeter frame 232 to maintain itssurface integrity and allows light fixture 102 to be used without aprotective coating or further surface treatments.

In the foregoing description, certain terms have been used for brevity,clearness, and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes and are intended to be broadlyconstrued. Moreover, the description and illustration of the inventionis an example and the invention is not limited to the exact detailsshown or described. Modifications and alterations of those embodimentswill be apparent to one who reads and understands this generaldescription. The present disclosure should be construed as including allsuch modifications and alterations insofar as they come within the scopeof the appended claims or equivalents thereof. Throughout thedescription and claims of this specification the words “comprise” and“include” as well as variations of those words, such as “comprises,”“includes,” “comprising,” and “including” are not intended to excludeadditives, components, integers, or steps.

1-20. (canceled)
 21. A light fixture for a controlled environmentceiling application, the light fixture comprising: an enclosure thatincludes an aluminum housing and a lens frame; an LED light sourcecarried by the enclosure; the LED light source being mounted directly tothe aluminum housing such that the housing functions as a conductiveheat sink for the LED circuit board.
 22. The light fixture of claim 21,wherein the aluminum housing includes an integral aluminum LED mountthat defines a substantially vertical surface when the light fixture ismounted in the ceiling; the LED light source being mounted to thesubstantially vertical surface of the integral aluminum LED mount. 23.The light fixture of claim 22, wherein the aluminum housing defines aplurality of fins used to increase surface area of the housing to removeheat from the housing.
 24. The light fixture of claim 23, wherein thehousing includes an extruded aluminum envelope disposed between firstand second aluminum end caps; the extruded aluminum envelope definingthe plurality of fins.
 25. The light fixture of claim 24, wherein theextruded aluminum envelope defines a plurality of channels; the end capsbeing secured to the envelope with threaded fasteners that engage thechannels.
 26. The light fixture of claim 25, wherein each of the endcaps defines a slot; the envelope having first and second ends disposedin the slots of the ends caps; and a sealing material disposed in theslots between the envelope ends and the end caps.
 27. A light fixturefor a controlled environment ceiling; the light fixture comprising: anenclosure having a lens frame sealed to a housing; the housing having amounting surface adapted to engage the ceiling when the light fixture isinstalled; the housing having a height above the mounting surface of nomore than two inches; and an LED light source disposed within theenclosure.
 28. The light fixture of claim 27, further comprising an LEDpower supply carried within the enclosure and a light guide plate havinga plurality of edges; the light guide plate being disposed above thelens frame of the enclosure; the LED light source being arranged todirect light into an edge of the light guide plate.
 29. The lightfixture of claim 27, wherein the lens frame includes a lens and whereinthe LED light source is arranged to direct light in a directionsubstantially perpendicular to the lens of the lens frame.
 30. The lightfixture of claim 27, wherein the lens frame includes a lens and whereinthe LED light source is arranged to direct light in a directionsubstantially parallel to the lens of the lens frame.
 31. The lightfixture of claim 27, wherein the mounting surface is an upwardly-facingmounting surface adapted to be disposed below the ceiling when the lightfixture is installed; and further comprising a gasket carried by thehousing; the gasket having a first portion for sealing the housing tothe ceiling when the light fixture is installed in the ceiling; thefirst portion of the gasket being disposed on the upwardly-facingmounting surface.
 32. A light fixture for a controlled environmentceiling; the light fixture comprising: an enclosure having a lens frameand a housing; the housing adapted to fit into one of a 1×2, 2×2, and2×4 light opening defined by a 2.0″ T-bar grid ceiling; and an LED lightsource disposed within the enclosure.
 33. The light fixture of claim 32,wherein the enclosure can be mounted to ceilings formed from othersystems including gypsum and panel systems.
 34. The light fixture ofclaim 32, further comprising an LED power supply carried within theenclosure and a light guide plate having a plurality of edges; the lightguide plate being disposed above the lens frame of the enclosure; theLED light source being arranged to direct light into an edge of thelight guide plate.
 35. The light fixture of claim 32, wherein the lensframe includes a lens and wherein the LED light source is arranged todirect light in a direction substantially perpendicular to the lens ofthe lens frame.
 36. The light fixture of claim 32, wherein the lensframe includes a lens and wherein the LED light source is arranged todirect light in a direction substantially parallel to the lens of thelens frame. 37-44. (canceled)
 45. A light fixture for a controlledenvironment ceiling; the light fixture comprising: an enclosure having alens frame and a housing; an LED light source disposed within theenclosure; and the lens frame having a lens carried by a stainless steelperimeter frame; the perimeter frame having a plurality of corners andan outwardly-facing surface exposed to the controlled environment whenthe light fixture is installed; the corners of the stainless steelperimeter frame being free of welds.
 46. The light fixture of claim 45,wherein the housing has an upwardly-facing mounting surface used tomount the light fixture to the ceiling; a gasket having a first portiondisposed on the upwardly-facing mounting surface to seal the housing tothe ceiling; and the stainless steel perimeter frame engaging thegasket.
 47. The light fixture of claim 45, wherein the entireoutwardly-facing surface is free of welds.
 48. A light fixture for acontrolled environment ceiling; the light fixture comprising: anenclosure that includes a housing and a lens frame; the housing havingan upwardly-facing mounting surface adapted to be disposed below theceiling when the light fixture is installed; an LED light sourcedisposed within the enclosure; an LED power supply disposed within theenclosure; a gasket carried by the housing; the gasket having a firstportion for sealing the housing to the ceiling when the light fixture isinstalled in the ceiling; the first portion of the gasket being disposedon the upwardly-facing mounting surface; a light guide plate disposedwithin the enclosure; the light guide plate having a plurality of edges;and the LED light source arranged to direct light into an edge of thelight guide plate; and the light fixture having a symmetric/asymmetriclight distribution pattern.
 49. The light fixture of claim 48, whereinthe lens frame includes a lens; the lens having the symmetric/asymmetriclight distribution pattern.
 50. The light fixture of claim 48, whereinthe light guide plate has the symmetric/asymmetric light distributionpattern.
 51. The light fixture of claim 48, further comprising adiffuser disposed below the light guide plate; the diffuser having thesymmetric/asymmetric light distribution pattern.